The present invention relates to a prosthetic leg.
Leg prostheses are designed to enable disabled persons to have a reasonable amount of mobility and activity. The simplest leg prosthesis is a peg leg, which enables a person to walk. Advances in the design of prosthetic legs attempt to mimic the biomechanics of those portions of the leg that are missing. Depending on the amputee""s circumstances, however, walking and sitting motions may be all that can be supplied in the prior art mechanics of prosthetic legs, especially with persons having above the knee (AK) amputations.
U.S. Pat. No. 4,883,493 issued to Martel et al. describes a prosthesis including a knee joint, a telescoping and resilient shank and a rigid foot prosthesis. Many other prosthetic designs incorporate a shock-absorbing design using sprints, elastomeric elements or compressible fluid elements. Most such designs are unsatisfactory because force dampening purposely inhibits the return of energy that stimulates normal walking momentum. Therefore, most shock absorbing designs do not function well. As well, prior art designs to include shock absorption are complex, increasing the weight and cost of the prosthesis, both of which are negative factors.
Prior art prostheses generally include a prosthetic foot that attempts to mimic the function of a human foot and ankle joint. Simpler foot prostheses include a bent resilient member which flexes somewhat. However, it is known that when pushing off in a walking motion, a foot becomes very rigid, therefore, a flexible artificial foot hinders normal walking motion. Complicated artificial ankles and feet have been devised, such as that disclosed in U.S. Pat. No. 2,657,393. However, such complicated designs are difficult to maintain and very costly.
It is also beneficial to allow some rotational movement between stump and heel strike. In natural walking gaits, there is considerable rotation in the heel, especially in relation to the hip. In U.S. Pat. No. 4,038,705 issued to Owens et al., a thrust bearing assembly is provided which allows limited rotational movement. However, the thrust bearing and a paddle element requires specially shaped elastomeric torque members to restrain over-rotation, which is perceived as being problematic in the prior art.
Therefore, there is a need in the art for a leg prosthesis that provides functionality in a biomechanically safe and sound manner, which is also simple and inexpensive in design and construction.
The present invention is directed to a jointless leg prosthesis having an axially reciprocating pylon and a rotational heel. The prosthesis is exceedingly simple and efficient in design, yet functions well in both walking and running movements. In one embodiment, the entire prosthesis comprises only 18 parts, which compares favourably against the complex and costly prior art designs.
Accordingly, in one aspect, the invention comprises a leg prosthesis for use by a leg amputee comprising: (a) a reciprocating pylon comprising first and second concentric pylons, where said first pylon comprises an insert fitted within the first pylon, wherein the first pylon and insert define a slot accommodating a pin affixed to the second pylon, and said first pylon closely fits and slides within the second concentric pylon to permit axial displacement between the first and second pylon; (b) an outer flange fitting affixed to the first pylon and having a inward facing cup; (c) an opposite flange fitting affixed to the second pylon and having an inward facing cup; (d) a coil spring extending between and fitting within the opposite facing cups; (e) a pedestal having a lower ground-engaging surface that supplies 360 degree rotation at heel strike, and an upper surface defining a cylindrical opening; (f) an adapter affixed to the second pylon, said adapter having a lower circular disc fitting closely within the pedestal cylindrical opening; wherein the insert and adapter each comprise a low-friction material such that additional lubrication or seals are not required.